Anti-spin hydraulic brake system

ABSTRACT

The present invention provides an apparatus and method of utilization thereof of a traction control system for automotive vehicles. The inventive traction control system provides selective hydraulically actuated braking to a drive wheel which is spinning to restrain rotation thereof so that torque to that respective wheel may be increased.

FIELD OF THE INVENTION

The field of the present invention is that of traction control systems.More particularly, the present invention provides an apparatus andmethod of utilization of the same to control wheel "spinning" due tohigh vehicle acceleration or driving on surfaces with exceptionally lowcoefficients of fiction.

DISCLOSURE STATEMENT

To maximize the traction of a vehicle drive wheel it is sometimesnecessary to retard the speed of the vehicle wheel to keep the wheelfrom spinning. Wheel spinning can often occur when a vehicle accelerateson an icy surface or when the vehicle undergoes high acceleration.

Prior to the present invention the major method to prevent vehicle wheelspin was some type of engine control. One method to retard engine torqueoutput is to reduce the number of active cylinders in the engine.Another method was to cut off fuel to the engine or to retard enginespark timing. Both of the above methods were disadvantageous in that theinertia of the drive train was still quite high. Therefore torque levelsof the drive wheels remain higher longer than desired, even though theengine may have slowed down. Still another disadvantage is thatmodulating the engine timing or fuel supply often cause the engine tooperate in a rough manner.

Still another disadvantage of relying upon engine control to retardvehicle wheel spin is that occasionally, especially on icy surfaces, twowheels on a common differential can have radically divergent wheelrotational speeds, therefore retarding the engine does not necessarilymean that the wheel whose rotational speed needs to be lowered will beso in comparison with the other wheel on the common differential.Furthermore, retardation of the engine lowers the maximum torqueavailable to the drive wheel which is not spinning.

To provide a better traction control system it is preferable toselectively brake the vehicle wheel which is spinning. Such a system asdescribed above must provide a fast response causing activation of thebrakes as soon as practically possible after the occurrence of acondition which causes wheel spin. Secondly, it would be advantageous toprovide a traction system which can not only apply braking to a spinningdrive wheel but can also modulate the application of the braking to thewheel. Furthermore, such a system should provide a brake overrideallowing the vehicle operator to hydraulically override the tractioncontrol system by activating the brake pedal. Additionally, it would bepreferable that the traction control system be able to be used with orwithout an anti-lock or anti-skid braking system (ABS). It would also beadvantageous that a traction control system rely upon hydrauliccomponents as much as possible to minimize the required electrical orelectronic components. Lastly it would be advantageous that such atraction control system could be used advantageously on two wheel orfour wheel drive vehicles as well as larger vehicles, such as class 8trucks.

SUMMARY OF THE INVENTION

To meet the above-noted and other desires the present invention isbrought forth. The present invention provides a traction control systemwhich can selectively brake a wheel which is in a spinning condition.Additionally, the present invention provides a traction control systemwhich can be overridden by the operator activation of the brakes.

It is a desire of the present invention to provide a traction controlsystem and a method of utilization thereof.

It is an object of the present invention to provide a traction controlsystem for a vehicle having a plurality of powered wheels, with at leasttwo of the wheels having fluid actuated brakes, the system also having amaster cylinder responsive to the command of a vehicle operator tosupply fluid to the wheel brakes, the traction control system includinga first mechanical hydraulic system for selectively supplyingpressurized brake fluid to a respective wheel brake or withdrawing brakefluid from respective wheel brake independent the master cylinder,sensing means to determine the rotational displacement of the respectivewheel and means to compare the wheel rotational displacement with thedisplacement of the vehicle and to generate a signal in responsethereto, a first control valve means normally closed allowingcommunication between the first mechanical hydraulic system and thewheel brake in response to the signal from the sensing means, isolatingvalve means, normally opened allowing fluid communication between therespective wheel brake and the master cylinder to allow operatoractuation of the wheel brake, the isolating valve means in a closedposition preventing fluid communication between the wheel brake and themaster cylinder when the first mechanical hydraulic system is incommunication with the wheel brake, means to hydraulically latch theisolation valve means to the closed position when the first mechanicalhydraulic system is supplying or withdrawing brake fluid from the brakecylinder, hydraulically-actuated means to override the first controlvalve means to return the isolating valve means to the open positionwhereby the operator can again control the wheel brakes.

It is also an object of the present invention to provide a tractioncontrol system for a vehicle having a plurality of powered wheels withat least two of the wheels having a fluid actuated brakes, the systemalso having master cylinder responsive to the command of a vehicleoperator to supply fluid to the wheel brakes, the master cylinder havinga powered booster, the system including a sump for storing a hydrauliccontrol fluid, an accumulator for storing the control fluid underpressure, a pump for transferring the control fluid from the sump tosaid accumulator, a piston body housing fluidly connected with theaccumulator and to the master cylinder booster, the piston body housinghaving a piston slidably mounted therein for selectively supplyingpressurized brake fluid to or withdrawing fluid from a respective wheelbrake independent of the master cylinder, a sensor/computer to determinethe rotational displacement of the wheels and to compare said wheelrotational displacement with the displacement of the vehicle and togenerate a signal in response thereto, a first solenoid control valvenormally closed allowing selective fluid communication between theaccumulator and the piston body housing in response to a signal of thesensor/computer, a second solenoid control valve normally open allowingselective fluid communication between said piston body housing and thecontrol fluid sump in response to a signal of the sensor/computer, anormally open shuttle isolation valve slidably mounted within the pistonbody housing allowing fluid communication between the respective wheelbrake and the master cylinder and preventing fluid communication betweenthe master cylinder and the wheel brake when the first solenoid valve isin an open position or when the second solenoid valve is closed, meansto hydraulically latch the shuttle isolation valve in a closed positionwhen the first solenoid valve is open or when the second solenoid isclosed, means to hydraulically open the shuttle isolation valve allowingthe master cylinder to communicate with the wheel brake by virtue ofpressure provided by the brake cylinder booster on the shuttle isolationvalve whereby the vehicle operator can again control the operation ofthe vehicle brake regardless of the opening of the first solenoid valveor the closing of the second solenoid valve.

It is yet another object of the present invention to provide a method toprevent wheel spinning in a motor vehicle having at least two poweredwheels with fluid actuated brakes and a master cylinder responsive tothe command of a vehicle operator, the system including selectivelysupplying or withdrawing brake fluid from a respective wheel brakeindependent of the master cylinder, sensing the rotational displacementof a respective powered vehicle wheel and comparing the speed with thedisplacement of the vehicle and generating a signal in response thereto,selectively controlling in response to the sensor signal supplying orwithdrawing of brake fluid to the wheel brake independently of themaster cylinder, isolating the wheel brake from the master cylinder whenthere is brake fluid being supplied to or withdrawn from the wheel brakeindependently of the master cylinder, hydraulically latching theisolating of the wheel brake from the master cylinder, and hydraulicallyoverriding the supplying or withdrawing of brake fluid to the brakecylinder independent of the master cylinder and opening thecommunication between the master cylinder and the wheel brake wherebythe operator can again control the operation of the wheel brakes.

Further objects, desires and advantages of the present invention canbecome more apparent to those skilled in the art as the nature of theinvention is better understood from the accompanying drawings and adetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the braking system of the present invention inthe environment of a four wheel drive vehicle with front disc and reardrum brakes;

FIG. 2 is a sectional view of a control valve body; and

FIG. 3 is a sectional view of a piston valve body.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 1, 2 and 3, the vehicle traction control system 7 hasa double circuit master cylinder 10. One master cylinder circuit 12 isutilized for the front brake cylinders 9 and the other master cylindercircuit 14 is utilized for the rear brake cylinders 5. An optionalbooster 20 is provided to reduce the pedal 30 effort of the operator toactuate the brakes. Additionally, connected with the system 7 is a brakefluid sump or reservoir 24 for returning brake fluid to the mastercylinder 10.

A control system fluid sump 25 is fluidly connected with a tractioncontrol pump 27 which feeds accumulator 22. Typically the hydrauliccontrol fluid has a higher viscosity than the brake fluid. The hydraulicaccumulator 22 is fluidly connected to a respective first control valve40 means or block for each hydraulic brake of the vehicle which is partof the traction control system 7.

The control valve block 40 (FIG. 2) has two plugged outlets 41 and ableeding port 43. The control valve block 40 also has an accumulatorinlet 45 and two additional fluid connections 46 and 47. Controlling thevalving of pressurized fluid through the accumulator inlet 45 is a firstsolenoid control valve 61. A normally open second solenoid control valve62 fluidly controls access between the first control valve block 40 andthe control fluid sump 25 via connection 47. When the first solenoid 61is open and the second solenoid 62 is closed, pressurized control fluidflows from the accumulator 22 to the displacement connection 46 via thefirst control block 40. If desired, an orifice 48 can be inserted withinthe first control valve block 40 to limit the flow rate. To shut offflow from the accumulator 22 the normally closed first solenoid 61returns to its closed position. To provide fluid communication betweenthe connection 46 and the sump 25, the second solenoid 62 is placed inan open position while solenoid 61 remains closed.

Referring in more detail to FIG. 3, excepting the bleed lines 51, theactuator or piston body housing 50 has five fluid connections. As shownpiston body housing 50 is for one separate wheel, however, if desired,it can be sized to handle a plurality of powered wheels. At the rightend, as shown in FIG. 3 at the bottom, is a connection 52 which fluidlycommunicates with the master cylinder circuit 14 via line 42. Towardsthe middle portion of the piston body housing 50 is a connection 53which fluidly communicates with a line 21 (FIG. 1) which is in turnconnected with booster 20 of the master cylinder 10. Next to the boosterconnection 53 is a connection 54. Connection 54 fluidly communicateswith the the sump 24 via line 56 (FIG. 1) and a check valve 55 to allowbrake fluid flow into the piston body housing 50 while preventing brakefluid flow from the piston body housing 50 towards the brake fluid sump24. At the far left is a displacement connection 57 which is fluidlyconnected with the displacement connection 46 of the control valve block40.

Slidably mounted within the piston body housing 50 is a displacementpiston 60 spring biased towards the connection 57. The piston 60 isslidably and sealably mounted on a shuttle valve extension 68. Thespring 65 which biases the piston 60 towards the connection 57 contactsa shuttle valve housing 70.

The shuttle valve extension 68 has a stem 69 with a head 63. The shuttlevalve housing 70 has a series of axial passages 72 generally alignedwith the bore of the piston body housing 50. The shuttle valve housing70 also has an inner bore 73 with a slidably sealably mounted shuttlevalve 74. The shuttle valve 74 has a head 75 for reception of a stud 66of the shuttle valve extension 68. Additionally, the shuttle valve 74has a reduced diameter section 76 which is non-sealably slidably mountedwithin an axial bore 82 of an intermediate housing 80 which is adjacentto the shuttle valve housing 70. The reduced diameter 76 of the shuttlevalve is adjacent to a ball valve member 91 of the ball check valve 90.The ball 91 is spring biased towards the shuttle valve and normallyallows fluid communication between the master cylinder via connection 52and the respective wheel cylinder via a connection 58 and line 15 (FIG.1). The valve 90 is provided with an housing 92 which mounts the spring93 which biases the ball 91 away from closing off the passages 94 and 95between the wheel cylinder 5 and the master cylinder 10. In the absenceof any control fluid pressure to the left of piston 60, the check spring93 of the valve 90 will place the ball 91 on opposite ball seat 87, awayfrom closing off the passages 94 and 95 between the wheel cylinder 5 andthe master cylinder 10.

The pump 27, control accumulator 22, in cooperation with piston 60provide a mechanical hydraulic system for selectively supplyingpressurized brake fluid to the wheel brakes or withdrawing brake fluidfrom the wheel brakes independent of the master cylinder. Check valve 90in cooperation with the shuttle valve 74 provides a normally openisolation valve means to allow fluid communication between the mastercylinder 10 and brake cylinder 5 to allow operator actuation of thebrakes. The isolation valve means when closed prevents fluidcommunication between the brake 5 and master cylinder 7. The isolationvalve means will be closed whenever the mechanical hydraulic system iscommunicating with the brake cylinder 5 as will be later explained.

Control valve block 40 in cooperation with solenoids 61 and 62 provide afirst control valve means allowing fluid communication between themechanical hydraulic system and the wheel brake in response to a signalfrom a sensor/computer 100 (FIG. 1).

In normal operation (non activation of the traction control system 7)the first solenoid valve 61 will be closed thereby preventing anycontrol fluid flow between the accumulator 22 and the displacementconnection 46, or to the sump 25. The displacement connection 57 (FIG.3) will be fluidly connected with the control fluid sump 25 via thecontrol block 40 since the second solenoid 62 is normally open. Thespring 93 of the valve 90 will bias the ball 91 against the opposingseat 87.

When the vehicle operator activates the brake pedal 30, brake fluid fromthe master cylinder 10 (via circuit 14, line 42 and connection 52 passesthrough the passages 94 and 95 towards the ball 91. The brake fluid thenexits to the wheel cylinder 5 via connection 58. The wheel cylinder 5 isconnected with a wheel shoe of the drum brake.

When one of the vehicle's wheels starts to spin a sensor/computer means100 compares the rotational speed of the wheel with the speed of thevehicle. The sensor/computer 100 provides a signal to brake the wheel sothat maximum traction can be developed from that wheel. (Note: the abovemay be made by a comparison of rotational displacement or a derivativethereof with vehicle displacement or a derivative thereof or some typeof wheel rotational displacement comparison with an average value. Theword displacement as used in this application extends to the sensing ofderivatives.) The above signal causes the first solenoid 61 for therespective spinning wheel to open allowing pressurized fluid controlfrom the accumulator 22 to exit out the displacement connection 46 ofthe control valve block 40. Simultaneously, or before the above actionof solenoid 61 the second solenoid 62 will close preventing thedisplacement connection 46 from being exposed to the control fluid sump24. Thereafter control fluid will flow out into the displacementconnection 57 of the piston body housing 50 causing the piston 60 tocompress the spring 65 moving to the right. The influx of pressurizedcontrol fluid through connection 57 will also cause the shuttle valveextension 68 to also move to the right thereby causing the shuttle valve74 to move to the right. The shuttle valve 74 will push the ball 91 offthe seat 87 causing the ball 91 to nest on a seat 97. Thereafter brakefluid communication between the master cylinder 10 and the brakecylinder 5 will be cut off. Cutting off fluid communication between themaster 10 and wheel 5 cylinders is necessary to prevent any possiblecommunication with the brake fluid sump 24 (via the master cylinder 10).

Fluid communication now is between the right side of the piston 60flowing through the axial passages 72 in the shuttle valve housing 70through radial openings 88 of the intermediate housing 80 and around thesmaller portion 76 of the shuttle valve 74 to the respective wheelcylinder 5. The control and modulation of the application of the brakecylinder 5 is accomplished by synchronization of selective opening andclosing of the first solenoid 61 along with a selective opening andclosing of the normally open second solenoid 62. The above switchingcontrols the pressure which is applied to the respective brake cylindervia movement of piston 60 on the stem 69 of the shuttle valve extension68. Pressure modulation is usually desirable since typically the brakecylinder is initially fully applied to achieve wheel speed reduction.Then after in response to the signal from the sensor/computer 100 thebrake cylinder pressure is modulated keeping the wheel from stopping.

When the shuttle valve small diameter portion 76 moves to the rightmoving the ball 91 against the seat 97, the shuttle valve 74 will remainfixed against the ball 91 regardless of the pressure modulation providedby movement of piston 60. The pressure on the right side of piston 60multiplied by the area of the left side 77 of the shuttle valve head 75will always be greater (provided that the vehicle operator is notoperating the brakes) than the pressure within bore 73 multiplied by thearea of the right side 79 of the shuttle valve head 75. The aboveprovides the means to hydraulically latch the isolation valve means to aclosed position when the mechanical hydraulic system is supplying orwithdrawing brake fluid from the brake cylinder 5.

It is desirable that the system 7 operate such that any operatoractuation of the brake pedal 30 will override the traction controlsystem 7. When the vehicle operator activates the pedal 30 the pressurein the brake booster 20 increases. The pressurized brake fluid from thebrake booster 70 enters the piston housing 50 body through connection 53via line 21 and causes the shuttle valve 74 to move to the left when thebooster pressure is greater than the pressure on the right side ofpiston 60. Moving the shuttle valve 74 leftward allows the spring 93 topush the ball 91 of the valve 90 on its opposite seat 87 cutting off anyfluid flow from the right side of the piston 60 to the brake cylinderwhen the pressure in passages 94 and 95 equal the pressure in axial bore82. The above assures a smooth transition of pressure delivered to brakecylinder 5. Fluid communication is again restored between the mastercylinder 10 and the wheel cylinder 5. Simultaneously, actuation of thebrake pedal 30 will cause the first solenoid 61 to close and the secondsolenoid 62 to open thereby connecting the displacement connections 46and 57 with the control fluid sump 25. Therefore the piston 60 will moveleftward with the assistance of the spring 65. Leftward movement of thepiston 60 will contact head 63 to further urge the shuttle valveextension 68 in a leftward position and normal operation of the wheelbrakes can again occur.

If desired, connection 53 could be connected with line 42 to the mastercylinder within an imposed check valve in between. However, booster 20pressure is usually available in less time after movement of pedal 30than master cylinder pressure.

If the vehicle operator does not activate the brakes, the systemsensor/computer 100 will signal the first solenoid 61 to return to thenormally closed position and for the second solenoid 62 to return to thenormally open position to deactivate the traction system 7 when the slipcondition has been eliminated.

An advantage of the present inventive traction control system 7 is thatan anti-lock braking system (ABS) can be added to the present system ifdesired.

Check valve 55 is provided to allow "makeup" brake fluid to reenter thecontrol block housing 50 after piston 60 has moved leftward, check valve55 could optionally be branched off to line 42 depending on the designof the master cylinder.

The present system 7 also provides optionally a hydraulic lock parkingbrake by simply activating the first solenoid 61 and closing the secondsolenoid 62 thereby locking the wheel cylinder 5. If desired, additionalelectronics can be provided such that the first 61 and second 62solenoids will latch to open and closed respective positions. Thereforethe hydraulic parking brake will not require a continuous use of currentto connect the accumulator 22 with the wheel cylinder 5. Also secondsolenoid 62 if specified to be normally closed, could provide a parkinglock function and be acceptable with traction control.

Another embodiment, not shown, provides a piston with multiple outsidediameters mounted in a piston valve housing with multi-diametered bore.The above allow a multiplier affect (either positive or negative asdesired) to relate the control fluid pressure to the desired brakecylinder pressure under traction control.

The present invention provides a method to prevent wheel spinning in amotor vehicle having at least two powered wheels with fluid actuatedbrakes 5 and a master cylinder 10 responsive to the command of a vehicleoperator, said system including the steps of:

1. Selectively supplying or withdrawing brake 60 fluid from a respectivewheel brake 5 independent of the master cylinder 10;

2. Sensing 100 the rotational displacement of a respective poweredvehicle wheel and comparing the speed with the displacement of thevehicle and generating a signal in response thereto;

3. Selectively controlling 40 in response to the sensor signal thesupplying or withdrawing of brake fluid 60 to the wheel brake 5independently of the master cylinder 10;

4. Isolating 74,90 the wheel brake 5 from said master cylinder 10 whensaid there is brake fluid being supplied to or withdrawn 60 from thewheel brake 5 independently of the master cylinder 10;

5. Hydraulically latching the isolating of the wheel brake 5 from themaster cylinder 10; and

6. Hydraulically overriding the supplying or withdrawing of brake 60fluid to the wheel brake 5 independently of the master cylinder 10 andreopening the communication between the master cylinder 10 and the wheelbrake 5 whereby the operator can again control the operation of thewheel brake 5.

While an embodiment of the present invention has been explained, it willbe readily apparent to those skilled in the art of the variousmodifications which can be made to the present invention withoutdeparting from the spirit and scope of this application as it isencompassed by the following claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A traction controlsystem for a vehicle having a plurality of powered wheels, with at leasttwo of said wheels having fluid actuated brakes, said system also havinga master cylinder responsive to the command of a vehicle operator tosupply fluid to said wheel brakes, said traction control system incombination comprising:a first mechanical hydraulic system forselectively supplying pressurized brake fluid to a respective wheelbrake or withdrawing brake fluid from said respective wheel brakeindependent of said master cylinder; sensing means to determine therotational displacement of said respective wheel and means to comparesaid wheel rotational displacement with the displacement of said vehicleand to generate a signal in response thereto; a first control valvemeans normally closed allowing communication between said firstmechanical hydraulic system and said wheel brake in response to saidsignal from said sensing means; isolating valve means, normally openedallowing fluid communication between said respectively wheel brake andsaid master cylinder to allow operator actuation of said wheel brake,said isolating valve means in a closed position preventing fluidcommunication between said wheel brake and said master cylinder whensaid first mechanical hydraulic system is in communication with saidwheel brake, said isolating valve means including a valve member formaking contact on a valve seat to prevent fluid communication betweensaid master cylinder and said wheel cylinder, and said isolating valvemeans including a shuttle valve separate from said valve member formoving said valve member, said shuttle valve communicating with apressurized line separate from said master cylinder line communicatingwith said valve member; hydraulic means to latch said shuttle valvemeans to a position wherein said valve member is in a closed positionwhen said first mechanical hydraulic system is supplying or withdrawingbrake fluid from said brake cylinder; and hydraulically-actuated meansto override said first control valve means to return said isolatingvalve means to said open position, said hydraulically-actuated meansincluding moving said shuttle valve to allow said valve member to returnto an open position whereby there is again fluid communication betweensaid master cylinder and said brake cylinder and whereby said operatorcan again control said wheel brakes.
 2. A traction control system asdescribed in claim 1 wherein said pressurized line communicating withsaid shuttle valve means is connected with said master cylinder.
 3. Atraction control system as described in claim 2 where said mastercylinder has a booster and line communicating with said shuttle valvemeans is connected with said booster.
 4. A traction control system for avehicle having a plurality of powered wheels with at least two of saidwheels having fluid actuated brakes, said system also having a mastercylinder responsive to the command of a vehicle operator to supply fluidto said wheel brakes, said master cylinder having a powered booster,said system in combination comprising:a sump for storing a hydrauliccontrol fluid; an accumulator for storing said control fluid underpressure; a pump for transferring said control fluid from said sump tosaid accumulator; a piston body housing fluidly connected with saidaccumulator and to said master cylinder booster, said piston bodyhousing having a piston slidably mounted therein for selectivelysupplying pressurized brake fluid to or withdrawing fluid from arespective wheel brake independent of said master cylinder; asensor/computer to determine the rotational displacement of saidrespective wheel and to compare said wheel rotational displacement witthe displacement of said vehicle and to generate a signal in responsethereto; a first solenoid control valve normally closed allowingselective fluid communication between said accumulator and said pistonbody housing in response to a signal of said sensor/computer; a secondsolenoid control valve normally open allowing selective fluidcommunication between said piston body housing and said control fluidsump in response to a signal of said sensor/computer; a normally openisolation valve mounted within said piston body housing allowing fluidcommunication between said respective wheel brake and said mastercylinder and preventing fluid communication between said master cylinderand wheel brake when said first solenoid valve is in an open position orsaid second solenoid valve is closed, said isolation valve including avalve member, communicating with said master cylinder, for makingcontact on a valve seat to prevent fluid communication between saidmaster cylinder and said wheel cylinder, and said isolation valveincluding a shuttle valve separate from said valve member for movingsaid valve member, said shuttle valve communicating with a pressurizedline from said master cylinder booster separate from the master cylinderline communicating with said valve member; hydraulic means to latch saidshuttle valve in a position wherein said valve member in a closedposition when said first solenoid valve is open or when said secondsolenoid is closed; means to hydraulically move said shuttle valve toposition said valve member to allow said master cylinder to communicatewith said wheel brake by virtue of pressure provided by said brakecylinder booster on said shuttle valve whereby said vehicle operator canagain control the operation of said vehicle brakes regardless of theopening of said first solenoid valve or the closing of said secondsolenoid valve.